Event ID 4999 is logged and MSExchangeServicesAppPool crashes in Exchange Server 2013

Applies to: Exchange Server 2013 EnterpriseExchange Server 2013 Standard Edition


In a Microsoft Exchange Server 2013 environment, MSExchangeServicesAppPoolcrashes frequently, and you see the following error in the Application log:

Log Name:      Application
Source:        MSExchange Common
Date:          Date and Time
Event ID:      4999
Task Category: General
Level:         Error
Keywords:      Classic
User:          N/A

Watson report about to be sent for process id: 1124, with parameters: E12, c-RTL-AMD64, 15.00.1104.005, w3wp#MSExchangeServicesAppPool, M.Exchange.Services, M.E.S.W.DispatchByBodyElementOperationSelector.CheckWcfDelayedException, System.NotImplementedException, 66d7, 15.00.1104.003.


This issue occurs because the size limit of a history conversation file is 1 megabyte (MB). When this limit is reached, Lync 2010 or Lync 2013 (Skype for Business) can't upload the conversion to Exchange Server 2013 through EWS. In this situation, the EWS application pool crashes.


To resolve this issue, make sure that all Lync clients are updated with the November 10, 2015, security update (KB3101496) for Lync 2013 (Skype for Business). Lync 2010 clients will have to first be upgraded to Lync 2013 (Skype for Business) and then updated with the November 2015 security update KB3101496. 

More Information

Lync 2013 .hist files are not written to Exchange Server through EWS when the file is larger than 1 MB. Instead, all the files accumulate in the history spooler folder and are never pushed to Outlook.

Users must close conversation windows before this limit is reached. The end user does not know when this limit will be reached, but 1 MB does represent a significant volume of data related to the conversation. In any case, users should close the conversation window once per day or whenever they're not actively using the conversation window.